This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Engine design has changed in response to environmental regulations, as government agencies enforce increasingly stringent limits on engine emissions. Starting in 2008, the United States Environmental Protection Agency will further restrict the levels of nitrogen oxides (NOx), carbon monoxide (CO), and non-methane hydrocarbon (NMHC) emitted by certain types of combustion engines. To meet these requirements, many types of engines now include pre-chambers. These devices ignite the fuel-air mixture inside the engine's cylinders with a flame from secondary combustion inside the pre-chamber. During the compression stroke of the engine, the pre-chamber is loaded with a relatively rich fuel-air mixture. To initiate combustion, this richer fuel-air mixture is ignited in the pre-chamber, rather than ignition being initiated by directly igniting the leaner fuel-air mixture in the cylinder. The resulting flame propagates from the pre-chamber into the cylinder, combusting the fuel in the cylinder more completely, and more rapidly, producing fewer undesirable emissions.
Many engines built prior to the adoption of recent environmental regulations do not include pre-chambers, and generally do not address emissions-related concerns. As a result, there is a large installed base of engines that may not satisfy newer emissions regulations. Replacing these installed engines with newer designs that include pre-chambers to reduce emissions would be expensive. Accordingly, to control emissions, for instance, it would be useful to find a way to retrofit the older engines with pre-chambers. Older engines, however, often do not have sufficient space above the cylinder heads to receive a pre-chamber, as the cylinder heads were designed with relatively small sparkplug wells to couple directly to spark plugs, which are typically smaller than pre-chambers.